Though all 398 passengers on board had a miraculous escape even as the pilot noticed the ``fire warning'' alarm mid-way through the flight, an hour-long, mid-air drama preceded the full ``emergency landing'' here, according to airport sources.

The jet was flying at 33,000 feet on a cleared Dubai-Singapore route. When the aircraft was flying at about 170 nautical miles east of the Chennai airport, the Air Traffic Control tower authorities here received a ``May Day'' call on the emergency RT channel, the sources said.

Within minutes of their hearing the SOS, the air traffic controllers, established contact with the pilot and told him that he could set course to Chennai. Consequently, all operational agencies were alerted and a full emergency was declared for the aircraft to make a landing.

But when the aircraft was flying at 80 nautical miles east of the airport, the pilot sought Chennai ATC permission to hover for some more time, saying the ``fire warning alarm light had gone off''. However, a few minutes later, he again radioed a ``May Day'' call, seeking clearance to set course for returning to Chennai and land on a priority basis.

At one stage, the sources said, the Emirates Airlines jet, with the ``fire warning'' emergency in the cargo-hold, made a steep descent at more than 6,000 feet a minute, putting on hold all other traffic at different points mid-air and keeping the air traffic controllers on tenterhooks for nearly an hour.

Later officials of the Regional Controller of Air Safety began a probe into the cause of the fire.

An independent enquiry by an engineering team of the Emirates Airlines from Mumbai and Dubai has collected material evidence.